linux-kernel - [PATCH 20/49] mm: migrate: Drop the misplaced pages reference count if the target node is full

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Date:	Fri,  7 Dec 2012 10:23:23 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Ingo Molnar <mingo@...nel.org>
Cc:	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paul Turner <pjt@...gle.com>, Hillf Danton <dhillf@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Alex Shi <lkml.alex@...il.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 20/49] mm: migrate: Drop the misplaced pages reference count if the target node is full

If we have to avoid migrating to a node that is nearly full, put page
and return zero.

Signed-off-by: Hillf Danton <dhillf@...il.com>
Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 mm/migrate.c |   17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index a2c4567..49878d7 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1489,18 +1489,21 @@ int migrate_misplaced_page(struct page *page, int node)
 		}
 		isolated = 1;
 
-		/*
-		 * Page is isolated which takes a reference count so now the
-		 * callers reference can be safely dropped without the page
-		 * disappearing underneath us during migration
-		 */
-		put_page(page);
-
 		page_lru = page_is_file_cache(page);
 		inc_zone_page_state(page, NR_ISOLATED_ANON + page_lru);
 		list_add(&page->lru, &migratepages);
 	}
 
+	/*
+	 * Page is either isolated or there is not enough space on the target
+	 * node. If isolated, then it has taken a reference count and the
+	 * callers reference can be safely dropped without the page
+	 * disappearing underneath us during migration. Otherwise the page is
+	 * not to be migrated but the callers reference should still be
+	 * dropped so it does not leak.
+	 */
+	put_page(page);
+
 	if (isolated) {
 		int nr_remaining;
 
-- 
1.7.9.2

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